This invention relates to a method of bonding a rod concentrically in a tubular shaft.
One obvious method of securing a rod in a tubular shaft is to coat the rod and/or the inner circumference of the shaft with a suitable cement or bonding agent, and then insert the rod in the shaft. However, this method suffers from the disadvantage that the bonding agent employed tends to rub off the rod when the rod is inserted into the shaft if too tight a fit is provided, or, alternatively, is accompanied by leakage of the bonding agent from the annular space between the rod and the shaft if the fit is too loose. In any event, the end result is a loss of bonding agent and a weakening of the joint, so that the desired degree of bonding is not attained. Furthermore, in certain instances, as in the case of the bonding of a universal joint fitting in a drive shaft, it is essential that the fitting be aligned concentrically in the shaft, and this method does not provide for obtaining a secure joint having such concentric alignment.
Another method of bonding a rod in a tubular shaft that has been proposed is to first insert the rod into the shaft, and then inject the bonding agent into the annular space between the rod and the shaft from a hole in the side of the shaft. A second hole in the side of the shaft is also necesssary in such case, of course, to allow for the release of air displaced by the bonding agent. However, not only is this technique quite slow, but oftentimes it fails to completely fill the annular space between the rod and the shaft with bonding agent, resulting in voids between them and a poor bond. Visual inspection of the joint, of course, is not possible, so that the presence of such voids, and the resulting poor bond, goes undetected.